NTSB Identification: LAX07LA040.
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Accident occurred Monday, November 20, 2006 in San Jose, CA
Probable Cause Approval Date: 09/27/2007
Aircraft: Stinson 108-1, registration: N97949
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

According to the pilot, he was flying above hilly terrain southeast of the airport when he heard a loud bang, followed by a violent vibration coming from the engine. The pilot added that the engine did not experience a total loss of power, but performed poorly due to the severe vibration. The pilot reduced the throttle and the vibration subsided, but when he added more throttle the violent vibration returned. The pilot then decided that it was unsafe to continue the flight and began searching for a place to land. He made a forced landing in a pasture, which was uneventful until one of the main landing gear contacted a "deviation" in the ground. The airplane nosed over and came to rest inverted. In a phone interview with the investigator-in-charge, a mechanic, who recovered the wreckage, reported that he examined the engine and discovered that the number 3 cylinder exhaust valve was stuck. The corresponding push rod tube was also bent, and the number 3 connecting rod was still intact.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Partial loss of engine power due to a seized exhaust valve during cruise flight. Rough terrain at the forced landing site was a contributing factor.

Full narrative available

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